Significance of saliva for the denture-wearing population

This paper summarises a series of studies already published in German and presents new data related to the aetiology of the 'dry mouth' and its associated problems.

AIMS

To study factors affecting mucous and serous salivary gland secretion, the aetiology of the 'dry mouth' and its associated problems, causative factors for hyposalivation and it's treatment.

SETTING

Two university dental hospitals.

SUBJECTS

587 denture wearers and 521 control subjects, and autopsy material.

INTERVENTIONS

Exercise, chewing, water, oestrogen, pilocarpine, and anetholtrithion therapy, biopsy of the minor glands.

MAIN OUTCOME MEASURES

Palatal secretion (PAL, microL/cm2/min) and parotid salivary flow (PAR), subjective complaints and clinical findings.

RESULTS

Resting flow rates for PAL between 0 and 65 microliters/cm2/min were seen in every age group. The flow rates of PAR (0 to 3.7 ml/10 min) were not correlated with PAL. Most patients with a resting flow rate of PAL < or = 6.0 microliters/cm2 suffer from a 'dry mouth' and Burning Mouth Syndrome (BMS) or oral dysaesthesia (OD) with or without chronic lesions of the oral mucosa. Etiological factors for the incidence of reduced PAL and associated problems include xerostomic drugs, oestrogen deficiency, radiotherapy, thyroid dysfunction, smoking or continuous wearing of complete upper dentures. PAL also correlated with the retention of upper complete dentures. PAL was correlated with the water content of epithelial tissues. PAL and PAR were both increased by drinking ample fluid, improving their circulation by physical exercises, chewing intensively, or taking oestrogens, pilocarpine, anetholtrithion.

CONCLUSIONS

Variation in palatal salivary secretion occurs and is clinically important.

Expression of the antimicrobial peptide, human beta-defensin 1, in duct cells of minor salivary glands and detection in saliva

The oral cavity is exposed to a variety of environmental insults. Salivary secretions play a critical role in maintaining oral health via innate host defense mechanisms and secretion of secretory IgA. Human beta-defensins (hBD) are antimicrobial peptides that are a component of the innate immune response; they are expressed in epithelia and are proposed to have a role in mucosal defense. hBD-1 mRNA is constitutively expressed in numerous mucosal tissues, including human gingiva and submandibular and parotid glands. Our objective was to detect the expression and localization of hBD-1 peptide in human salivary glands and in saliva. Minor salivary gland tissue was obtained from biopsies of patients with mucoceles (n = 20). hBD-1 peptide was detected by immunohistochemistry; expression was localized to the ductal cells and not the acinar cells of these glands. The peptide was located apically, toward the lumen in the duct cells. Further evaluation showed stronger hBD-1 expression in ducts with periductal inflammation, as indicated by the immunostaining of serial sections with anti-CD45 specific for B- and T-lymphocytes. Statistical analysis showed a strong correlation of hBD-1 staining and inflammation. Results of immunolocalization suggest that hBD-1 functions to protect salivary glands from retrograde infection, that expression of the peptide is enhanced in inflamed sites, and that post-transcriptional regulatory mechanisms may be involved in hBD-1 peptide expression. Western immunoblot analysis also detected hBD-1 peptide in unstimulated, whole, acidified saliva from normal volunteers. However, hBD-1 peptide associated with salivary mucin resulted in loss of the detection in a dot-immunoblot assay. Association of hBD-1 with salivary mucin may facilitate peptide distribution and adherence to oral surfaces and aid its function within the oral cavity.

Labeled neoglycoproteins and human lectins as diagnostic and potential functional markers in salivary glands of patients with Sjögren's syndrome

OBJECTIVE

The profile of glycans and their recognition by endogenous receptors (lectins) are increasingly attributed to disease process. Monitoring this can provide information on the pathogenesis of Sjögren's syndrome (SS). Commonly, plant lectins are employed for phenomenological glycan mapping. To go beyond this approach restricted to binding of exogenous probes, new markers measure ligand properties of glycans to human (not plant) lectins and the presence of sugar receptors completing a protein-carbohydrate recognition system. Carrier-immobilized sugar epitopes (neoglycoproteins) and purified human lectins establish this innovative panel.

METHODS

The host defence molecules mannan binding lectin, serum amyloid P component, and the macrophage migration inhibitory factor-binding sarcolectin, selected for their involvement in cell destructive mechanisms, were purified and labeled. The plant lectins SNA and MAA were employed to monitor regulation of potential ligand sites for I-type lectins and galectins. Asialofetuin was tested as a "pan-galectin selective" probe. The specific binding characteristics were determined by quantitative morphometry and statistical analysis.

RESULTS

Diagnostic information emerged from this analysis. The percentage of stained tissue area was significantly different between SS and control specimens after processing with GlcNAc and Man-bearing neoglycoproteins and the 2 tested serum lectins. For separation of cases of primary and secondary SS, the staining intensity with the asialoglycoprotein, sarcolectin, and the exogenous alpha2,6-sialylated glycan-binding lectin SNA was statistically significant.

CONCLUSION

Saccharide-presenting probes to measure the cellular capacity to bind glycan epitopes and human lectins as sensors for endogenous binding sites have proven to be useful as diagnostic tools. We suggest the differences we observed reflect aberrations from the normal cellular homeostasis with relevance for the pathogenesis of SS and its manifestation as a primary or secondary syndrome.

Cytokine mRNA expression in the labial salivary glands of healthy volunteers

OBJECTIVE

To examine the cytokine profile in minor salivary glands of healthy volunteers and examine differential cytokine production from acinar and ductal tissues.

STUDY DESIGN

Acinar and ductal elements were isolated by a cell-specific micro-dissection technique from frozen 8 microns sections of minor salivary glands from healthy volunteers. Reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern hybridization using 32P-labeled cytokine gene-specific probes were utilized to detect cytokine mRNA. mRNA transcripts for the Th1 cytokines (IL-2, TNF-alpha, and IFN-gamma), Th2 cytokines (IL-4, IL-6, and IL-10), TGF-beta, actin, and CD3 delta were analyzed in acini, ducts and total tissue sections of minor salivary glands of six healthy controls.

RESULTS

Actin, TGF beta and TNF alpha was present in 6/6 acinar, 6/6 ductal, and 6/6 total section samples. IFN gamma was present in 2/6 acinar, 3/6 ductal, and 6/6 total samples. IL-2 was found in 3/6 acinar, 3/6 ductal and 5/6 total sections. IL-6 was found in 1/6 acinar, 0/6 ductal, and 5/6 total sections. IL-10 was found in 3/6 acinar, 3/6 ductal, and 5/6 total sections. IL-4 was present in 0/6 acinar, 0/6 ductal and 1/6 total samples. CD3 delta was present in 6/6 acinar, 5/6 ductal and 6/6 total sections.

CONCLUSIONS

These results demonstrate abundant expression of cytokines in healthy minor salivary glands. The production of these cytokines in healthy tissues demonstrates a likely role of supporting normal cellular function.

Minor salivary gland secretion in the elderly

OBJECTIVE

Very little information exists on minor salivary gland output (MSGO) in health and disease. We investigated the minor salivary gland output of elderly subjects with different medical backgrounds and the relationship of that output with life practices, demographic variables, complaints of dry mouth, medication usage, functional status, medical treatments, and dental and medical variables.

STUDY DESIGN

MSGO was measured with a special moisture-detecting paper on the lip, cheek, and palate, which comprised the total MSGO. A parsimonious linear regression model was developed to determine which of the many measured variables influenced the MSGO.

RESULTS

There were significant differences in MSGO between the recruitment sites, with the non-Veteran Affairs (VA) Independent Living participants having significantly lower MSGO than the VA groups. A secretion rate for MSGO based on median values from all subjects of <4.6 microL/min was categorized as being low, whereas a secretion rate for MSGO >/=4.6 microL/min was categorized as high. A regression model was used to examine variables that could be associated with MSGO variability. The results show that being older, a woman, a current smoker, and having a complaint of dry mouth were associated with lower MSGO rates.

CONCLUSIONS

An association between subjective complaints of dry mouth and a decrease in MSGO measured objectively was demonstrated in this elderly population. Furthermore, age and sex effects on MSGO were also demonstrated.

Trefoil factor expression in normal and diseased human salivary glands

Trefoil factors are wound-healing peptides important in protection and healing of the human gastrointestinal tract. Their potential for therapy of gastrointestinal ulcers has been established. This study investigated the hypothesis that trefoil factors are also present in human salivary gland. Tissues from surgical biopsy specimens were collected fresh into ice and stored in liquid nitrogen. Breast, stomach, and colon constituted positive controls. Trefoil factor mRNAs were detected by reverse transcription polymerase chain reaction (RT-PCR) or by in situ hybridization (ISH) with formalin-fixed, paraffin-embedded sections. Amplified DNA fragments were ligated into pGEM-T Easy vector and used to transform competent Escherichia coli JM109, allowing sequencing to confirm identity of cloned fragments. Generation of amplifiable cDNA was confirmed using primers specific to the ubiquitously expressed abl gene. By RT-PCR, TFF1 (pS2) mRNA was detected in 14 of 15 glands, TFF3 (hITF) mRNA in 13, and TFF2 (hSP) in only 1 gland. ISH of 15 glands (7 of which had been studied by RT-PCR) showed the same pattern of expression and indicated that TFF1 mRNA was usually expressed at low levels by a few mucous cells, whereas TFF3 was produced abundantly by most mucous cells. There was no difference in patterns of expression comparing parotid, submandibular, and minor mucous glands. Nor was there an obvious relationship between trefoil factor expression and pathology, but those glands not expressing TFF1 or TFF3 had evidence of chronic inflammation or atrophy. Trefoil factors are likely to be important in healing, predisposition to, and therapy of, oral diseases.

Tumor-associated glycoprotein 72 (TAG-72) expression in salivary gland neoplasia: an immunohistochemical study using the monoclonal antibody (MAb) CC49

OBJECTIVES

The purpose of this study was to investigate immunohistochemically the expression of tumor-associated glycoprotein 72 (TAG-72) using the monoclonal antibody (MAb) CC49 in salivary gland neoplasia and normal salivary glands in an attempt to determine the potential usefulness of MAb CC49 in diagnostic and therapeutic applications.

MATERIALS AND METHODS

Eighty-six specimens (21 benign tumors, 41 malignant, and 24 normal salivary glands), fixed in 10% formalin and embedded in paraffin, were retrieved from the files of the Department of Oral Medicine and Oral Pathology at the Dental School of Aristotle University, Thessaloniki, Greece, and were retrospectively studied with hematoxylin and eosin and with the streptavidin-biotin-complex method using the MAb CC49.

RESULTS

Strong immunoreactivity for TAG-72 was observed in salivary duct carcinoma, adenocarcinoma, papillary cystadenocarcinoma, low-grade mucoepidermoid carcinoma, normal submandibular, sublingual, and minor salivary glands. Weak or no immunoreactivity was found in adenoid cystic carcinoma, basal cell adenocarcinoma, polymorphous low-grade adenocarcinoma, and normal parotid gland.

CONCLUSIONS

Our results suggest the potential use of MAb CC49 in the differential diagnosis of some salivary gland neoplasms in which their histopathologic features overlap, and in the radiation immunolocalization and immunotherapy of malignant tumors that are localized in the parotid gland.

Innervation pattern and Ca2+ signalling in labial salivary glands of healthy individuals and patients with primary Sjögren's syndrome (pSS)

We have characterised the innervation pattern and intracellular Ca2+-signalling in labial salivary glands (LSG) of 16 patients with primary Sjögren's syndrome (pSS) and 27 healthy controls. Numerous immunoreactive nerve fibers (IRF) containing vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide (PACAP) were found around acini, ducts and blood vessels. Substance P (SP)-, neuropeptide Y-, tyrosine hydroxylase- and nitric oxide synthase-IRF were mainly surrounding ducts and blood vessels. The majority of pSS patients had inflamed LSG and the presence of focal lymphocytic infiltrates (FI) were more frequent and pronounced as compared with healthy controls. In areas with normal or diffusely inflamed LSG tissue, pSS patients demonstrated the same distribution of IRF as healthy controls with similar histology. However, IRF were absent in central areas of FI both in pSS and age-matched healthy controls. Although all pSS patients had hyposalivation, stimulation with acetylcholine, norepinephrine, phenylephrine, isoproterenol, VIP, PACAP, SP, adenosine 5'-triphosphate and uridine 5'-triphosphate induced the same increase in the intracellular free Ca2+ concentration in LSG acini from both pSS patients and healthy controls, indicating the presence of functional receptor systems in vitro.

Immunohistochemical detection of insulin-like growth factor-I in the labial salivary glands of patients with Sjögren's syndrome

OBJECTIVE

The purpose of the present study was to investigate the presence of insulin-like growth factor-I (IGF-I) in the labial salivary glands of patients with Sjögren's syndrome and healthy controls and to determine if there are any differences between these two groups.

DESIGN

An immunohistochemical study.

SUBJECTS AND METHODS

Twenty-five patients with Sjögren's syndrome, 20 healthy controls and 20 patients with mucoceles of the lip were used in this study. All individuals underwent a systemic evaluation and a lip biopsy. Sections from the lip biopsies were stained with haematoxylin and eosin (H&E). Immunohistochemical staining was also performed using a three-step indirect immunoperoxidase for IGF-I.

RESULTS

The light microscopic examination revealed the presence of a mononuclear infiltration in the labial salivary glands of patients with Sjögren's syndrome. Most of the infiltrates were lymphocytes. Immunohistochemically an intense staining result was apparent in the same group. In contrast sections of labial salivary glands of healthy individuals and of patients with mucoceles revealed very weak staining.

CONCLUSIONS

The above findings and the fact that both lymphocytic infiltration and IGF-I were predominantly seen in ductal regions, suggest that IGF-I may be a target of autoimmunity in Sjögren's syndrome.

Existence and distribution of melanocytes and HMB-45-positive cells in the human minor salivary glands

The existence and distribution of melanocytes in the human minor salivary glands were investigated in a series of autopsy and biopsy materials. The cells with the following characteristics were regarded as melanocytes; spindle-shaped or dendritic cells with fine granular pigments: (i) stained brownish-black by hematoxylin-eosin stain, and black by Masson-Fontana's silver impregnation method; and (ii) disappeared after treatment with peroxide and potassium permanganate solution. In addition, the expression of antigen identified by anti-HMB-45 antibody in serial sections with melanocytes was examined. Melanocytes were found in eight (1.8%) of 445 cases, and there was no relationship between the existence of melanocytes and significant diseases of the subjects. Various numbers of melanocytes were distributed in fibrous tissue around the interlobular ducts, intralobular ducts and acini, but were not in direct contact with the epithelia. Neither melanocytes nor melanin granules were found in the salivary gland epithelia. HMB-45-positive cells without intracytoplasmic fine granules were found solitarily or in small groups in periductal and periacinar fibrous tissues with or without slight infiltration of small mononuclear cells.

Phenotypes in canalicular adenoma of human minor salivary glands reflect the interplay of altered secretory product, absent neuro-effector relationships and the diversity of the microenvironment

AIMS

Uncertainty about the factors influencing phenotypes in salivary canalicular adenoma prompted the present investigation.

METHODS AND RESULTS

Specimens of canalicular adenoma from 15 patients were examined with the use of histology, histochemistry for protein, mucosubstances and pigments, nerve staining and immunocytochemistry for cytoskeleton components. The tumours consisted largely of simple cells lining tubules that were occasionally cystic or branching and budding, and were set in loose, vascular and often haemorrhagic stroma. Other phenotypes recognized were mucous cells, apocrine-like cells, pigmented cells, microliths and stromal macrophages, detected in 26.6%, 20%, 33.3%, 20% and 53. 3% of the patients, respectively. Simple cells showed moderate levels of -SH groups and strong immunoreactivity for 'simple' epithelial phenotype cytokeratin. The simple cells lining cystic tubules showed additional immunoreactivity for 'stratified' epithelial phenotype cytokeratin, possibly an adaptation to mechanical pressure. Lumina showed variable levels of neutral and carboxylated glycoproteins, and chondroitin sulphate. Stroma showed high levels of chondroitin sulphate and hyaluronic acid. Mucous cells showed high levels of -SS- groups and nonsulphated glycoproteins. Apocrine-like cells contained lipofuscin. Pigmented cells contained haemosiderin, possibly a consequence of localized iron overload. Microliths contained mucosubstances. Macrophages often contained lipofuscin. No nerves were found in relation to the tumours.

CONCLUSIONS

The results suggest that, contrary to popular belief, phenotypes in canalicular adenoma do not reflect histogenetic concepts but rather may derive from the interplay between an altered secretory product, consisting of glycosaminoglycan and an immature form of glycoprotein, the lack of neuro-effector relationships and the different microenvironments throughout the tumour.

Biosynthesis of glycosaminoglycans and aggrecan by tumor cells in salivary pleomorphic adenoma: ultrastructural evidence

The present study attempted to discover the sites of synthesis of various glycosaminoglycans (GAGs) and aggrecan in salivary pleomorphic adenoma (PA) with the use of a highly sensitive and specific post-embedding immunogold-silver staining technique at the ultrastructural level. Silver particles representing various GAGs and aggrecan were found to accumulate frequently in the intercellular spaces of non-luminal cells in the epithelial clusters and were dispersed in the myxoid matrix of the mesenchyme-like areas. Furthermore, the non-luminal epithelial cells were demonstrated to contain immunopositive intracytoplasmic vesicles and vacuoles, some of which were of Golgi complex origin. In contrast, intracellular silver particles for hyaluronic acid were mostly attached to the inner surface of the cell membrane. These observations agree well with the current theories of the biosynthesis of GAGs and proteoglycans and provide direct evidence for the production of various GAGs and aggrecan by tumor epithelial cells of PA. Such findings support the ideas that in PA a loss of epithelium occurs by stromalization following epithelial secretion of extracellular matrix substances and transformation of epithelium to mesenchyme represents the basic principle of the tissue heterogeneity in this tumor.

Sialic acid residues in the labial salivary glands from Sjögren's syndrome patients

OBJECTIVE

To investigate the composition and expression of sialic acid in the labial salivary glands (LSG) in Sjögren's syndrome (SS).

METHODS

LSG of 19 patients with primary SS (n = 11) or secondary SS (n = 8) were studied. Specimens from 7 healthy women served as controls. Computer-assisted microscopy was employed to quantitatively determine the percentage of positive structures, the staining intensity and the heterogeneity for the 4 biotinylated plant lectins Tritricum vulgaris L. (WGA), Maackia amurensis (MAA), Sambucus nigra (SNA) and Canavalia ensiformis L. (Con A).

RESULTS

In the acini there was a significant decrease in the staining heterogeneity of WGA in SS compared to controls; the same was observed with respect to MAA staining in the connective tissue and extralobular ducts. In the intralobular ducts, primary SS differed from normal and secondary SS mainly in terms of a decrease in the percentage of positively labeled MAA tissue. In addition, Con A stained acinar cells were significantly more numerous in secondary SS compared with primary SS.

CONCLUSION

Differences in the degree of glycoconjugate sialylation were found in SS labial salivary glands, and may play a role in the disease process.

CD4 cytotoxic and dendritic cells in the immunopathologic lesion of Sjögren's syndrome

The existence of CD4+ T lymphocytes with cytotoxic activity in minor salivary gland (MSG) biopsies from Sjögren's syndrome (SS) patients was investigated using in situ double immunohistochemistry technique. The presence of dendritic cells (DC) in SS lesions was examined by using single and double immunohistochemistry methods and a panel of different MoAbs to specific cell surface markers (i.e. CD3, CD11c, DRC). Furthermore, the ultrastructural morphology of DC was characterized by electron microscopy (EM). Immunogold labelling technique using the DRC surface marker was also applied. Finally, we investigated the existence of germinal centres (GC) in the salivary gland lesions of SS patients. Seven patients with primary SS and five patients with non-specific sialadenitis were the subjects of this study. Our results indicate the existence of a CD4+ cytotoxic cell population that utilizes perforin-mediated cell destructions as they expressed perforin mRNA. Quantitative analysis of these cells revealed that they comprised approximately 20% of the existing T lymphocytes. We also identified a population of CD4+ T cells that expressed the CD11c activation marker. Furthermore, we observed a distinct cell subtype which expressed the DRC cell surface marker. These cells had the characteristic ultrastructural morphology of DC and were DRC+ when examined by immunoelectron microscopy. Finally, the formation of GC structures in the histopathologic lesions of the salivary glands was observed. The above findings indicate that both CD4+ cytotoxic T lymphocytes (CTL) and DC may be involved in the initiation and perpetuation of SS pathogenesis. Moreover, the formation of GC in the lesions reveals a possible mechanism for in situ differentiation and proliferation of activated B lymphocytes.

Primary Sjögren's syndrome (pSS): subjective symptoms and salivary findings

We studied the relationship between dry mouth, general health and objective findings in 16 patients having primary Sjögren's syndrome (pSS) according to the 1993 European classification criteria as well as in healthy controls. Serum autoantibody to SSA/SSB (AB) was correlated to unstimulated whole saliva flow (UWS) and labial salivary gland focus score (FS). All patients had dry mouth symptoms and UWS < or = 0.10 ml/min, but patients with UWS < 0.05 ml/min and AB had more complaints of oral and ocular dryness. These patients also tended to have more exocrine and non-exocrine manifestations, and oral dryness had a greater impact on their self-reported general health than in patients with UWS > or = 0.05 ml/min. Accordingly, we consider rating of oral dryness by visual analogue scales or categorised questionnaires to be valuable for the evaluation of oral involvement in pSS.

Detection and quantification of MUC7 in submandibular, sublingual, palatine, and labial saliva by anti-peptide antiserum

The large carbohydrate moiety of low-Mr salivary mucin MUC7 (originally referred to as MG2) is subject to variations. Biochemical analysis and quantification of MUC7 in saliva samples require recognition tools that are independent of the carbohydrate moiety. Therefore, we have evoked three antisera to synthetic peptides of MUC7. One of these (CpMG2), raised against the C-terminal peptide, recognized native MUC7 in saliva and was characterized further. Recognition of MUC7 by CpMG2 turned out to be specific, resistant to dissociating and reductive treatments, and independent of glycosylation differences, as indicated by Western analysis and ELISA. The antiserum could be used to monitor MUC7 during purification procedures. MUC7 was demonstrated in small volumes of saliva from all (sero)mucous glands, including the palate and lip. Analysis with antibodies and lectins indicated large variations in amount as well as in glycosylation of MUC7. An ELISA was developed to determine the relative quantity of MUC7 in the glandular salivas: mean values of approximately 220, 980, and 100 microg mucin per mL were found in submandibular, sublingual, and palatine saliva, respectively.

Cytokine expression in human labial minor salivary gland epithelial cells in health and disease

Microdissection of biopsy material from labial minor salivary glands followed by RT-PCR demonstrates extensive production of cytokines IL-2, 1L-6, IL-10, TNF-alpha, TGF-beta, and IFN-gamma in both normal glands and in glands affected by Sjögren's syndrome. Continuation of these studies should expand our knowledge of normal salivary gland function and the pathogenesis of Sjögren's syndrome.

Study of saliva secretion and the salivary fluoride concentration of the human minor labial glands by a new method

Unstimulated and stimulated flow rate from minor lower labial glands and the fluoride concentration of resting whole and labial saliva were measured over 15 min using a novel method avoiding eversion of the lips. Resting salivary flow rate was measured as 1.09+/-0.44 microl/min/cm2 and stimulated flow rate as 3.13+/-1.05 microl/min/cm2. Secretion rates were significantly (p<0.001) increased during periods of continuous speaking. The increase in secretion elicited by labial movements and speaking may result from mechanical stimulation and/or activity of myoepithelial cells. Fluoride concentrations in resting whole saliva and in unstimulated minor labial gland saliva were 0.066+/-0.048 and 0.181+/-0.073 parts/10(6), respectively. The secretory capacity of the minor labial glands and the high F concentration in their secretions suggests a significant contribution to the F content of whole saliva. Our non-invasive method permits collection from the minor labial glands of a volume large enough for chemical analysis. It should prove useful for studying the effects of different secretory stimuli.

Secretion from minor salivary glands following ablation of the major salivary glands in rats

Since minor salivary glands are tiny and dispersed, ductal cannulation cannot be used when studying their function. The present study was devised to develop a method of measuring minor salivary gland function by excision of the major glands. Female rats (230-280 g) were anaesthetized with sodium pentobarbital. Ablation of the submandibular, sublingual and parotid glands was performed through a sagittal neck incision. Sham-operated rats served as controls. Groups of sialadenectomized animals were investigated immediately and after 1 week, 2 weeks and 3 months. To study secretory function, the mouth was rinsed with 250 microl water in every 5 min and protein and amylase concentrations were measured. After an initial 50 min of basal secretion pilocarpine (1 mg/kg, i.p.) was given. Bilateral ablation of both submandibular, sublingual and parotid glands led to a moderate loss of body weight and a considerable increase in water intake. No other obvious abnormality was observed for periods up to 90 days following surgery. We deduce that the minor glands secrete approximately 14 % of protein and 1% of amylase in whole saliva Secretion is maintained even after 90 days following removal of the major glands. Surgical removal of the major salivary glands allows the secretory function of the minor glands in rats to be studied in vivo.

The flow rate and composition of human labial gland saliva

Since the flow rate of saliva from human labial salivary glands has usually been measured as the secretion from an area of labial mucosa as 0.05-4.8 microl/cm2/min. The only data for single glands gives a comparable figure of 0.1 microl/min/gland. There is no consensus on the effects of gustatory stimulation, gender or ageing, although most reports suggest that flow rate is not related to gender and ageing up to age 60. The main differences in composition between labial gland saliva and that from the major glands are the higher and variable sodium concentration, the very low phosphate and hydrogen carbonate concentrations, and the higher protein concentration despite low concentrations of amylase. The concentrations of IgA and blood group substances are notably higher in labial gland saliva. In Sjogren's syndrome and cystic fibrosis flow rates are decreased. Low rates of flow have been associated with a higher incidence of dental caries.

Immunocytochemical localisation of neuropeptide-containing nerve fibres in human labial glands

Different neuropeptide-containing nerve fibers (vasoactive intestinal polypeptide, substance P, neuropeptide Y) and nitric oxide synthase (NOS) positive nerve fibers were investigated to clarify their role in the function of human labial glands using immunohisto- and immunocytochemical techniques. The distribution pattern of all immunoreactive nerve fibers was similar both in the control and in the Sjögren's syndrome specimens. A large number of thin varicose vasoactive intestinal polypeptide and NOS positive nerve fibers were seen around or in close contact with the acini. Some of the immunoreactive nerve fibers were associated with the salivary ducts and blood vessels. Substance P and neuropeptide Y immunoreactive nerve fibers were located mainly around the blood vessels. Immunocytochemistry demonstrated that some of the positive nerve fibers were in direct contact with the acini, blood vessels and with the lymphocytes. The gap between the membranes of immunoreactive nerve terminals and the target cells was 40 to 200 nm. The number of the nerve terminals in Sjögren's syndrome specimens was decreased and some degenerated axons were also found. These results suggest that these neuropeptides and nitric oxide might act as a neurotransmitter in the regulation of secretion and blood flow in the labial glands. These fibers might also alter the neuroimmunological processes, because the investigated neuropeptides are known to be immunoregulators.

Ion transport and signalling in human labial glands

Recent reports characterizing the physiological properties of normal human labial acini are reviewed with particular emphasis on mechanisms related to fluid secretion. In contrast to the salivary glands of several experimental animals, human labial acinar cells do not appear to have a1-adrenergic receptors, substance P peptidergic receptors, or significant levels of Cl-/HCO3- exchange. Nor do they appear to secrete HCO3- in response to Ca2+ mobilizing stimuli. The data presently available indicates that fluid secretion by these glands is mainly under muscarinic control and is due to acinar Cl- secretion driven by a basolateral Na+ -K+ -2Cl- cotansporter.

Expression of aquaporin 1 (AQP1) water channels in human labial salivary glands

Aquaporin (AQP) water channels are widely expressed in the membranes of fluid-transporting epithelia. Despite the fact that salivary glands are the site of considerable water movement, relatively little is known about the role of aquaporins in human salivary glands. We have examined the expression of AQP1 in human parotid, sublingual and labial salivary glands. Total RNA was extracted from glandular tissue obtained from surgery or biopsy. The presence of AQP1 mRNA was demonstrated in each of the three glands by RT-PCR using primers specifically designed for human AQP1. The PCR product from the labial gland RNA was further amplified with nested primers and the sequence confirmed by automated fluorescent DNA sequencing. The cleaned first PCR product from these glands was then used as a 32P-labelled hybridization probe in a Northern analysis which confirmed the presence of significant amounts of AQP1 transcript in all three glands. AQP1 expression was also demonstrated in cryosections of human labial glands by immunohistochemistry using peroxidase-linked antibodies. Antibody labelling was most prominent in the capillaries but was also evident in the basal regions of the labial gland acini, and may therefore be associated with the serous demilunes which are believed to be a significant site of fluid movement.

Morphological features of the minor salivary glands

The minor salivary glands are important components of the oral cavity, present in most parts of the mouth, and their secretions directly bathe the tissues. Individual glands are usually in the submucosa between muscle fibres, and consist of groups of secretory endpieces made up of mucous acinar cells and serous or seromucous demilune cells. The ductal systems comprise intercalated ducts, intralobular ducts usually lacking basal striations, and excretory ducts opening directly through the mucosa Minor glands secrete highly glycosylated mucins, containing blood group determinants, and probably active in tissue lubrication and bacterial aggregation. They also secrete several antimicrobial proteins and immunoglobulins, and the lingual serous (von Ebner's) glands secrete digestive enzymes and proteins with possible taste perception functions. Minor gland morphology and function can conveniently be studied in the rat. There are substantial differences between major and minor salivary glands, as well as among the minor glands, in the nature and composition of their mucous and serous secretory products. The role of minor salivary glands in the function and defence of the oral cavity may be better understood as a result of new physiological and molecular methods applicable to samples of limited size and availability.